Mainly, however, people seem simply to not understand it. Why would America’s warriors — for that matter, why would anyone — urinate on a dead body?

I spent a year, off and on, with a platoon of U.S. soldiers in the Korengal Valley of eastern Afghanistan. There was a lot of fighting, a lot of casualties and an enormous amount of stress on the men I was with. I never saw anyone do anything like this, but then again, I never saw any dead Taliban fighters — the enemy always recovered their casualties before we could get there.

Nevertheless, the things the soldiers shouted during combat were very revealing of the state of mind that war produces. (For the record, I’m sure the Taliban was screaming pretty much the same things about us.) At one point a Taliban fighter had his leg shot off during a firefight and was crawling around on the hillside, dying, and the men I was with cheered at the sight. That cheer deflated me. I liked these guys tremendously, but that celebration was just so ugly. I didn’t want them to be like that.

Later, I asked one of them about it, and he explained that they had been happy because they were that much closer to all going home alive. They weren’t cheering the enemy’s death; they were cheering their own lives. That particular fighter would never again be able to kill an American soldier.

Yet, I can’t imagine that there was a time in human history when enemy dead were not desecrated. Achilles dragged Hector around the walls of Troy from the back of a chariot because he was so enraged by Hector’s killing of his best friend. Three millennia later, Somali fighters dragged a U.S. soldier through the streets of Mogadishu after shooting down a Black Hawk helicopter and killing 17other Americans. During the frontier wars in this country, white Americans routinely scalped Indian fighters, and vice versa, well into the 1870s.

The U.S. military should be held to a higher standard, certainly, but it is important to understand the context of the behavior in the video. Clearly, the impulse to desecrate the enemy comes from a very dark and primal place in the human psyche. Once in a while, those impulses are going to break through.

There is another context for that behavior, though — a more contemporary one. As a society, we may be disgusted by seeing U.S. Marines urinating on dead Taliban fighters, but we remain oddly unfazed by the fact that, presumably, those same Marines just put high-caliber rounds through the fighters’ chests. American troops are not blind to this irony. They are very clear about the fact that society trains them to kill, orders them to kill and then balks at anything that suggests they have dehumanized the enemy they have killed.

But of course they have dehumanized the enemy — otherwise they would have to face the enormous guilt and anguish of killing other human beings. Rather than demonstrate a callous disregard for the enemy, this awful incident might reveal something else: a desperate attempt by confused young men to convince themselves that they haven’t just committed their first murder — that they have simply shot some coyotes on the back 40.

It doesn’t work, of course, but it gets them through the moment; it gets them through the rest of the patrol.

There is a final context for this act in which we are all responsible, all guilty. A 19-year-old Marine has a very hard time reconciling the fact that it’s okay to waterboard a live Taliban fighter but not okay to urinate on a dead one.

When the war on terror started, the Marines in that video were probably 9 or 10 years old. As children they heard adults — and political leaders — talk about our enemies in the most inhuman terms. The Internet and the news media are filled with self-important men and women referring to our enemies as animals that deserve little legal or moral consideration. We have sent enemy fighters to countries like Syria and Libya to be tortured by the very regimes that we have recently condemned for engaging in war crimes and torture. They have been tortured into confessing their crimes and then locked up indefinitely without trial because their confessions — achieved through torture — will not stand up in court.

For the past 10 years, American children have absorbed these moral contradictions, and now they are fighting our wars. The video doesn’t surprise me, but it makes me incredibly sad — not just for them, but also for us. We may prosecute these men for desecrating the dead while maintaining that it is okay to torture the living.

I hope someone else knows how to explain that to our soldiers, because I don’t have the faintest idea.

Sebastian Junger, a contributing editor at Vanity Fair, is the author of “War” and the director of the 2010 film “Restrepo,” both of which chronicle the experiences of U.S. troops fighting the war in Afghanistan.

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